Effects of alternative establishment systems on resource availability, understorey composition and tree performance in juvenile hybrid poplar plantations
Goehing, J., B.R. Thomas, S.E. Macdonald and E.W. Bork. 2017.
Abstract
The effects of different understorey management practices on tree-weed dynamics and associated tree
establishment were investigated in newly planted hybrid poplar plantations containing Walker poplar (Populus
deltoides × (P. laurifolia × P. nigra)) and its progeny Okanese poplar (Walker × (P. laurifolia × P. nigra)). Trees
were established in 2012 on a research site in northeastern Alberta using one of four treatments: business-
as-usual (BAU; herbicide, tillage, then planting), extended fallow (BAU additional tillage and herbicide before
planting), a cover crop interseeded on BAU areas, and a no-till treatment where trees were planted directly
into sod receiving prior chemical weed control but no tillage. Tree survival and growth, herbaceous vegetation
cover and composition, soil conditions (N availability, water content and temperature), together with light
availability, were measured over three consecutive growing seasons (2012-2014). Okanese outperformed
Walker in all treatments and was more responsive to vegetation control, indicating greater plasticity and
potential for short-rotation-intensive-culture plantations. Further, tree performance was improved by
extended chemical and mechanical (fallow) site preparation prior to tree planting. This treatment resulted in
sustained control of understorey vegetation, in particular competitive perennial forbs and graminoids, and
increased light and nutrient availability to trees. These results also highlighted the importance of controlling
perennial rather than annual herbaceous competitors prior to and during plantation establishment.
